Discussion

Interventional catheterisation for ductus arteriosus is now first-line treatment in patients ranging from very small premature infants to patients in the ninth decade of life. ^{Reference Galeczka, Szkutnik and Bialkowski1} In some patients with a nonrestrictive ductus arteriosus, the increased flow and pressure to the pulmonary circulation can lead to elevated pulmonary vascular resistance. However, this is unusual in children < 2 years of age without associated cardiac or non-cardiac abnormalities. ^{Reference Khositseth and Wanitkun2}

Increased pulmonary vascular resistance constitutes a therapeutic dilemma. Closure of the ductus arteriosus may not prevent progressive pulmonary vascular disease and right heart failure, and some patients may exhibit worse symptoms than they would have if the PDA had remained open. ^{Reference Rigby3} Vasoreactivity testing and the advent of “pulmonary hypertension medications” that can be used before and/or after intervention have added levels of complexity to the treatment decision. ^{Reference Myers, Tissot and Beghetti4} While there are no perfect criteria for when to intervene (by percutaneous devices or surgery), a combination of clinical, imaging, and haemodynamic parameters is used to predict the probability of favourable short-term results. ^{Reference Rosenzweig, Abman and Adatia5}

Recommended thresholds for ductus arteriosus repair in the presence of pulmonary hypertension have included: a baseline pulmonary vascular resistance of < 4 WU/m2 and pulmonary-to-systemic vascular resistance ratio of < 0.3–0.33. ^{Reference Balzer, Kort and Day6} Conversely, defect repair has been contraindicated when there is a pulmonary vascular resistance index of > 8 WU/m2 or a pulmonary vascular resistance of > 4.6 WU. Parameters in between these extremes have required individualised evaluation, often with pulmonary vasoreactivity testing. ^{Reference Rosenzweig, Abman and Adatia5}

Temporary occlusion of the ductus arteriosus, generally with a balloon catheter, allows the acute evaluation of its effect on pulmonary arterial pressure, particularly in borderline cases. ^{Reference Bhalgat, Pinto and Dalvi7} The use of an interventional device instead of a balloon for temporary occlusion testing is effective and safe, and it offers the advantage of avoiding an extra step, as well as reducing the cost of the procedure in resource-limited settings. This was demonstrated in adult patients by Yan et al, using Amplatzer duct occluder and Amplatzer muscular ventricular septal defect occluder (ADO and AMVSDO, AGA Medical Corporation, Golden Valley, Minnesota, USA) devices. ^{Reference Yan, Zhao and Jiang8}

The parameters that have been considered favourable for closure after performing vasoreactivity testing or temporary ductus occlusion have included: a decrease of 20% in the pulmonary vascular resistance, a decrease of 20% in the pulmonary-to-systemic vascular resistance ratio, a pulmonary vascular resistance < 6 WU/m2 or a final resistance ratio < 0.3. ^{Reference Lopes, Barst and Haworth9} Patients with a pulmonary vascular resistance > 9 WU/m2, breathing 100% oxygen, have been considered poor candidates for defect repair. ^{Reference Vijayalakshmi, Setty and Narasimhan10} Table 2 summarises the experience of several investigators in paediatric patients with hypertensive ductus arteriosus. ^{Reference Niu, Mallory and Justino11–Reference Zabal, García-Montes and Buendía-Hernández14}

Table 2. Device closure of hypertensive ductus arteriosus: studies in paediatric patients

Abbreviations: Ao = aorta; PVRI = pulmonary vascular resistance index; WU/m2 = Wood units per square metre of body surface area; mo = months; y = years; PAP = pulmonary arterial pressure; SP = systemic pressure; PH = pulmonary hypertension; RV = right ventricle; ADO = Amplatzer Duct Occluder; AMVSDO = Amplatzer Muscular Ventricular Septal Defect Occluder; ASO = Amplatzer Septal Occluder (AGA Medical Corporation, Plymouth, Minneapolis, United States of America).

Our patient was diagnosed with a large ductus arteriosus at an early age and at low altitude. She underwent a catheterisation at higher altitude, where she had an elevated pulmonary vascular resistance. A Nit-Occlud PDA-R device was used to perform the temporary occlusion test (keeping it attached to the cable) simultaneously with hyperoxia. There was a significant decrease in pulmonary arterial pressure. The same device, which had a minimum stent diameter 3 mm larger than the ductus diameter, was released and remained in stable position. The estimated pulmonary pressure by echocardiography was normal at the two-year visit, at which time the sildenafil was discontinued. The contribution of her return to live near sea level with respect to her normalisation of pulmonary arterial pressure remains unclear.

Our patient had a significant drop in pulmonary arterial pressure with temporary device test occlusion and we proceeded with device release. However, the exact threshold criteria for when to proceed with closure of hypertensive ductus arteriosus remain to be determined. Experience with larger numbers of patients who have vasodilator testing, temporary occlusion, and treatment with pulmonary hypertension medications before and after intervention will be necessary to better determine the criteria for ductal closure.

In conclusion, we describe successful use of a device to temporarily test-occlude and then permanently close a hypertensive ductus arteriosus in a 3-year-old patient.

Figure 1. Images of the cardiac catheterization procedure. (a) Angiogram demonstrating the ductus arteriosus. (b) Placement of the device in the ductus arteriosus. (c) Angiogram after 30 minutes of test occlusion and hyperoxia, device still attached. (d) The device after release.